The Mississippi state flag is displayed with the banners of other U.S. states, territories and commonwealths, above a walkway in the tunnel from the Capitol Building to the Dirksen Senate Office Building in Washington on July 1, 2016. (J. Scott Applewhite/Associated Press)

After President Trump declared his intention to leave the Paris climate agreement, three Democratic state governors announced that their states would continue to pursue efforts to reduce greenhouse gas emissions. Meanwhile, Republicans in Congress vowed to enact federal laws to preempt state and local immigration policies at odds with the GOP agenda. This contradicts conventional wisdom, which holds that Republicans promote states’ rights while Democrats want more policymaking power concentrated at the federal level.

Is this a partisan reversal on states’ rights? Our research suggests not. Rather, both parties have historically promoted or preempted states’ rights depending on their party’s political goals for a given issue.

Both Democrats and Republicans care about states’ rights

The United States has a federal system, which means that state and federal governments divide and share power to make and enforce laws. As the chart below shows, the federal government has a long history of enacting laws that preempt, or limit, states’ and localities’ policymaking powers.

But federal preemption jumped sharply in the 1970s and again over the past decade. About 6 percent of federal laws enacted between 2000 and 2009 preempt state and local powers, compared with about 3.5 percent during the previous decade.

Federal preemptions by decade

How we did our research

To learn more about how the parties at the national level approach states’ rights, we surveyed every federal law enacted between 1990 and 2012 that preempted state power in some way. As the figure below shows, we found that both parties have contributed relatively equally to the dramatic increase in federal preemption.

Preemption statutes enacted, by party control of House and presidency, 1990-2012

Over about the past 20 years, Republicans in Congress and in the White House have been just as willing to limit state power as have Democrats. For example, Presidents Bill Clinton and George W. Bush each signed 64 preemption statutes into law during their respective eight years in office. Similarly, between 1990 and 2012, no matter which party controlled the House of Representatives, roughly the same average number of preemption policies became law each year.

Parties preempt states’ rights in different ways

However, exactly how they limit state authority varies, in keeping with the parties’ different political goals.

The parties enact different types of preemptions. Republicans are more likely to impose what are known as “ceiling preemptions.” These laws cap the amount of regulation states can enact on a particular issue. For example, a ceiling preemption might prohibit states from setting new or more stringent emissions standards for a particular industry.

Democrats, by contrast, are much more likely to limit state power by setting floor preemptions, or minimum standards that states must meet but can exceed if they want to. For example, such a law might set a federal emission standard for a particular industry but allow states to enact tougher emissions standards.

As shown in the charts below, we find that when Democrats controlled the House between 1990 and 2012, 57 percent of preemption laws enacted were floors. By contrast, when Republicans controlled the House, 33 percent of laws enacted with preemption statutes were floors; the remaining 67 percent were ceilings limiting state regulatory power.

Floor vs. ceiling preemptions as enacted by party control of House, 1990-2012

You can see this illustrated in the partisan gap between floor and ceiling preemptions in public health and consumer safety. When Democrats controlled the House, 75 percent of preemptions were floors, compared with 36 percent of those passed under Republican majorities. That means that Democrats in Congress used preemptions to create a base level of health and safety regulation across the states — while Republicans did so to limit state authority to regulate in this area.

For example, the Card Act of 2009, enacted under Democratic control, created new credit card rules to protect consumers but left states able to add still more regulations. By contrast, a Republican-led 2001 amendment to the Consumer Product Safety Act introduced federal regulations for electric bicycles that explicitly overrode more stringent state laws.

States’ rights in the Trump era

States’ responses to Trump and the current Republican agenda are entirely consistent with these patterns, as the parties’ stands on states’ rights vary with the issue at hand.

But in the ongoing debate over the federal Medicaid program that funds health care for low-income and disabled people, the tables are turned. Many Republicans want to shift toward block grants, which would let each state decide how to run and fund its Medicaid program. Predictably, Democrats are opposed; they want enough federal control to ensure that current benefits are protected.

The sides flip once more on immigration. Congressional Republicans want to preempt state power to prevent Democratic cities from becoming sanctuary cities. Meanwhile, congressional Democrats are fighting to protect state and local rights to resist Trump administration policies against sanctuary cities.

In sum, neither party holds a principled position on whether to preempt or protect states’ rights. Instead, both parties use federal power to limit state authority or to promote it depending on their party’s policy goals. Expect to see such strategic partisan use of federalism continue as the parties go to battle over Trump’s and the GOP’s agenda.

Mallory E. SoRelle is an assistant professor of government and law at Lafayette College, specializing in the study of American politics and public policy. Follow her on Twitter @SoRelleM.

Alexis N. Walker is an assistant professor of political science at Saint Martin’s University, with a focus on American politics and organized labor.